December 8, 2016

Annual crow stopover makes work for Facilities

Each year they come, choosing Pittsburgh as their winter vacation destination.

Thousands of American crows, seasonal guests from the north, descend in late October in cawing, swirling masses before scattering in February and March to nest farther north.

“It’s a fantastic sight,” said biological sciences faculty member Tony Bledsoe, who has grown accustomed to seeing the annual visitors settle into treetops and rooftops near the Clapp-Langley-Crawford complex.

Crows are social creatures. They live in small groups during the breeding season, which begins in March, but in fall they gather in large roosts. Pittsburgh has a resident crow population, but at this time of year it also is a destination for flocks of migrant birds from Canada, New York and Ohio.

Bird expert Kate St. John equated the gathering to a huge winter beach vacation for the birds. Crow families come with teenagers and little ones in tow — the previous year’s hatchlings help raise the next year’s brood.

And, for crows seeking to pair up for the spring breeding season, this is the place to meet, said St. John, author of the Birds Outside My Window blog.

Photo by Mike Drazdzinski/Photographic Services

Intelligent and tenacious, crows tend to roost in the same areas year after year. They can live 10-20 years, so “there are crows in the crowd that remember, crows that know,” St. John said.

She counted about 4,000 crows in a four-block area near Fifth and Bellefield avenues in early November; last year’s Christmas bird count found more than 25,000 crows in the city of Pittsburgh.

Migrant crows in recent decades have increasingly begun favoring urban roosts, which are a little warmer than the surrounding countryside, said Bledsoe. Well-lit areas with large trees offer protection from crows’ chief natural predator, the great horned owl, also an enemy of peregrine falcons.

Although the crows and the peregrines share a common enemy, the two usually don’t interact with each other. The raptors that nest atop the Cathedral of Learning “typically don’t bother with things below the 20th floor,” Bledsoe said. And the crows will have departed before Pitt’s peregrines begin their nesting.

Exactly why the crows choose Oakland isn’t known, but some years they’ve targeted Soldiers and Sailors Memorial Hall; other years they’ve chosen Ruskin Avenue as their hub, Bledsoe said.

This year, the scene is being played out along Fifth Avenue, where the crows have converged by the hundreds in the tall oaks that border the Cathedral of Learning lawn.

Photo by Tom Altany/Photographic Services

They adjourn predawn, fanning out across a 10-15-mile radius to feed. Toward nightfall they reconvene, squawking and swirling before settling into the treetops — just as evening commuters are departing Oakland.

If they follow form, they soon will move on to roost in the vicinity of Polish Hill and the Strip District before they head home in spring, Bledsoe said.

For some, the crows can’t be gone soon enough.

While they pose no danger — they don’t attack humans nor are they considered a vector or reservoir for disease that can spread to humans — their droppings foul sidewalks, buildings and vehicles.

“It’s not really bad unless you’re under the roost when they come at night or when they leave in the morning,” said Bledsoe.

They tend to “lighten the load” before taking flight, St. John said.

This year the crows also have taken up residence in the trees near Heinz Chapel, where they’ve created a smelly, slippery mess.

Heinz Chapel director Pat Gibbons is perturbed.
“It’s a terrible time for this,” she said, citing a busy schedule — including tonight’s Chancellor’s holiday concert — as well as weddings, rehearsals, tours, music lessons and worship services on the calendar this month.

Her pleas — “I didn’t want to have to be the one to have to deal with a bride whose dress had been dipped in it” — have brought Facilities Management to the rescue. They’ve been power washing the pavements, handrails and bus shelters — “Everything that’s under the birds” — several times a day, and plan to rent a small street cleaning machine to help clear the sidewalks, said Dan Fisher, assistant vice chancellor for operations and maintenance.

The University isn’t the only institution that’s become a destination for crows. At the state Capitol complex in Harrisburg, where roosting crows have been a nuisance for decades, Capitol police have been firing exploding shotgun shells to scare off, but not harm, the birds.

And Penn State announced that it would shoot pyrotechnic bangers and screamers to scare off roosting crows. According to a Nov. 9 media release, some 3,000 migrating crows roosted on Penn State’s main campus last year.

According to the Penn State Extension’s guide to managing urban crow roosts, pyrotechnics, distress calls, low-powered lasers, fogging agents and effigies are among the non-lethal harassment tactics that may encourage crows to roost elsewhere.

Facilities has been using a sound system in an effort to encourage the birds to move on. The recording, which includes sounds of the horned owl and of birds in distress, aims to make the crows uncomfortable enough to leave, Fisher said.

The unit is moved every day or two, and its start and stop times vary. “We have to keep mixing it up because they learn the patterns quickly,” he said.

Fisher said Pitt began using the recording several years ago with success, after consulting with the National Aviary.

This year, however, the spooky sounds seem to be more disturbing to unsuspecting humans than to the birds. “This year they don’t seem to be moving,” Fisher said. “We need to continue to disrupt them.”

Fisher said there are no plans to fire any pyrotechnics here, but the loud sounds of fireworks may be added to the arsenal of recordings, and more machines may be added, since the birds seem unwilling to go.

St. John said dissuading the crows early is key: “It’s harder to roust them out once they’ve become comfortable in a place.”